Preparation of a superhydrophilic and superoleophobic sponge for continuous oil/water and oil/oil separation

Oily wastewater produced from various industries and oil spills has posed serious threats to the environment and human health. Promisingly, superwetting materials emerge as great candidates for efficient oil/water separation. In this work, a superhydrophilic-superoleophobic melamine sponge was prepared using a facile immersion method. Methyltrimethoxysilane (MTMS) was used as a binder, which combined fluorosurfactant (FS-50) and TiO 2 onto the sponge surface. The coated sponge displayed a water contact angle of 0° and an oil contact angle of 154.5°. Accordingly, it exhibited absorption capacities of above 86 g/g for water and under 1 g/g for oils. Based on its selective permeability and 3D porous structures, the coated sponge could continuously separate various immiscible oil/water mixtures and oil-in-water emulsions with separation efficiencies larger than 99.4 % and 98.7 %, respectively. Notably, the superhydrophilic-superoleophobic sponge was extended to present opposite wettability towards polar and nonpolar liquids. Consequently, it achieved continuous separation of immiscible oil/oil mixtures, with separation efficiency over 99.1 %. Additionally, the coated sponge displayed excellent reusability, great mechanical stability against compression and abrasion, and stable separation performance for various harsh oil/water mixtures. The study presented a promising separation candidate for future applications in oily wastewater treatment and other liquid/liquid separation fields.